Transcriptional activator that binds specific DNA sequence. Functions as a response regulator involved in His-to-Asp phosphorelay signal transduction system. Phosphorylation of the Asp residue in the receiver domain activates the ability of the protein to promote the transcription of target genes. May directly activate some type-A response regulators in response to cytokinins. {ECO:0000250|UniProtKB:Q940D0}.